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This study describes a case of interspecific aggregation involving a spider's web and its effect on web architecture of another species of spider. On two transects of 100 m each, one with Nephila clavipes (Linnaeus 1767) webs and one without, we noted the spiders associated, or not, with N. clavipes webs, and compared the web architecture of the most commonly associated species, Leucauge venusta (Walckenaer 1842). The transect with N. clavipes contained more spiders in general than that without N. clavipes, most of which were L. venusta for both transects. The height above ground of L. venusta webs associated with N. clavipes presented a larger range of distribution, which closely mimicked that of N. clavipes webs except when the N. clavipes web was at ground level. Leucauge venusta webs were more inclined when in association with N. clavipes (49.4 ± 3.3° vs 20.4 ± 2.0°). We concluded that L. venusta clearly prefers to be associated with N. clavipes, and we discuss the possible advantages of this association. [ABSTRACT FROM AUTHOR]

Using two-dimensional gel electrophoresis, changes in protein phosphorylation caused by cyclic nucleotide-dependent protein kinases were analyzed with or without exposure to a protein kinase inhibitor, H-8, during the mouse sperm acrosomal reaction. The acrosomal reaction, induced by the treatment of sperm with dibutyryl cyclic AMP or dibutyryl cyclic GMP, was inhibited by H-8. The activities of cyclic AMP-dependent protein kinase (PKA) and cyclic GMP-dependent protein kinase induced by the sperm extract were also inhibited by H-8. When endogenous PKA in sperm was activated by the addition of cyclic AMP, a 45-kDa protein spot identified by electrophoresis indicated the occurrence of phosphorylation in vivo. Furthermore, the enhanced phosphorylation of the 45-kDa protein spot was inhibited by H-8. These results suggest that the PKA-catalyzed phosphorylation of the 45-kDa protein may be involved in the regulation of the mouse sperm acrosomal reaction. [ABSTRACT FROM AUTHOR]